In recent years, as digital cameras and other devices having color output have advanced, the technology has attempted to keep pace in order to record images on paper sheets or the like. The ultimate goal of such recorded images (“hard copy”) is silver halide photography, and it is desired to provide recorded images from such devices that have the color reproduction, image density, gloss, etc. as close to those of silver halide photography as possible.
The technology of inkjet color printing has attempted to keep pace with the development of digital cameras and other color output devices, but improvements are continually sought in order to be competitive with silver halide images.
Most coatings on print media used for color inkjet printing consist of discrete layers with dissimilar compositions. These compositions typically comprise one or more binders and one or more pigments. Binders are used to secure the pigment to the substrate or to a lower layer. Pigments are present in the binder as particles, and are used to form a porous medium for absorbing liquid from the ink. Thus, as the ink is printed on the print media, the uppermost layers serve to retain the ink colorant close to the surface, to maximize color gamut, while the lowermost layers serve to absorb the liquids in the ink to reduce dry time.
The foregoing approach is disadvantageous, however, as multiple raw materials and mixing vessels must be used to produce these coatings. Also, compatibility between layers must be designed or otherwise taken into account; otherwise, incompatibilities between layers may result. Examples of such incompatibilities include gelling and delamination.
There are competing issues that affect the nature and composition of the coatings formed on print media. It is desired that the coating adhere well to the supporting substrate. It is also desired that the coating exhibit good ink absorption characteristics. Often, an improvement of one of these properties causes a degradation of the other property, such that it is possible to have a coating composition that adheres well to the substrate, but has poor ink absorption characteristics, and vice versa.
Thus, there is a need for a coating that evidences both good adhesion to the substrate and good ink absorption.